There is a thread on IMSR. I have stated in my posts there that by giving up the breeder requirement, it is more likely to succeed. Support of ORNL makes it even more likely. Also, it will need clearance from Canadian and not the US NRC for initial building in Canada for softening the bitumen sands.
Success of any MSR will open the path for others including the thorium/Uranium breeders..

I find it hard to believe that we would be congratulating someone for giving up on the most compelling feature of the molten-salt reactor technology: the ability to implement, efficiently, the thorium fuel cycle.

As I said in comments about the Thorcon idea, crank up the centrifuges, because under the guise of "proliferation resistance" we're going to have to greatly expand world uranium enrichment capability if we want a world powered by ThorCons or IMSRs. We'll be making plenty of plutonium to go along with it too.

"Proliferation" is often thrown up by the ignorant as the reason to avoid the pure thorium cycle. But the reality is that any nuclear fuel cycle less than a breeder will rely on uranium enrichment, which is by far the easiest path towards obtaining weapons grade materials. The two breeder options (fast and thermal) let you choose between plutonium or uranium-233 as your basic fissile material, and uranium-233 has built-in features (like U-232) production that strongly, strongly discourage its use in anything other than power-generating reactors.

So I do not accept the premise that a reactor design that relies on uranium enrichment (which all non-breeders do) is a superior choice in terms of proliferation risk.

What do we tell the world? Crank up the enrichment cascades? Because if we want to power the world on ThorCons you're going to have to enrich a lot of uranium in a lot of different places.

Not giving up on it. David's a big fan of pure thorium cycle with two fluid, the whole shebang. That may be in the future.

Just getting priorities in order. Do you want MSR sooner or later? Perfect's the enemy of the good and all that. Any MSR is better than continuing to build coal plants.

Re proliferation. We should tell the world that proliferation is a fabricated and contrived argument that should not dictate our use or disuse of centrifuge technology or any nuclear technology for that matter. If you make proliferation important enough to dictate disuse of centrifuges, you're already on the bottom of the sea still wondering why your ship has sunk. Once you've helped torpedo centrifuges they will then turn on you and argue you're separating weaponizeable neptunium and partitioning it for the lowest bidder from Iraq.

Steel mills can make steel ingots and sheets for shovels or machineguns. Should we opt to ban steel mills in an effort to ban machineguns?

After 9/11 an anti-proliferationist might have expected or even demanded travel companies to be outlawed as they increase demand for weaponizeable passenger aircraft killing thousands and shocking the world. If you get dragged into this line of thinking its a losing battle.

I want an MSR done right. This same argument gave us the PWR and sixty years later we're still stuck with it. Does it matter much to us now whether the first PWR was built in 1957 or whether a thermal breeder had been built in 1967? We don't care anymore. We care about the fact that we were saddled with an unsustainable system that did not evolve into a sustainable one.

I am unconvinced that either IMSR, ThorCon, or WAMSR have the potential to evolve into an efficient thorium reactor. I am making hard choices in LFTR design to insure that early demonstrations are on a technology path to the real thing. IMSR and ThorCon are cutting corners on the fuel cycle, pushing hard choices off into the distant future, and will end up with an unremarkable product.

Me too. We likely have different ideas on right and wrong, that's all. A good MSR done is better than a perfect MSR not done.

This same argument gave us the PWR and sixty years later we're still stuck with it.

Good, then we know its an effective stratagem.

We care about the fact that we were saddled with an unsustainable system that did not evolve into a sustainable one.

All nuclear reactors are very sustainable. Its not a technology problem. Plenty of uranium around in the earth and sea, storing spent fuels is easy and done all the time. People don't care about sustainability, it is just a hollow buzzword that helps them promote their favorite tech and keep them blind to changing their world views in face of overwhelming evidence.

Cyril R wrote:We likely have different ideas on right and wrong, that's all.

We certainly do. A converter MSR that does not have a clear evolution to a thermal breeder is not an MSR "done right". Taking shortcuts on structural materials, salt compositions, and chemical processing is not "done right". Deploying spurious "proliferation" arguments in public fora about the value of the pure thorium fuel cycle is not helping anyone either.

I really don't understand what you and Jack are trying to do. You say you've made these choices to save the world from global warming but did not design a sustainable reactor and fuel cycle. You're going to make a lot of waste and the bigger problem is that most of it will be very difficult to deal with.

Cyril R wrote:We likely have different ideas on right and wrong, that's all.

We certainly do. A converter MSR that does not have a clear evolution to a thermal breeder is not an MSR "done right". Taking shortcuts on structural materials, salt compositions, and chemical processing is not "done right". Deploying spurious "proliferation" arguments in public fora about the value of the pure thorium fuel cycle is not helping anyone either.

I really don't understand what you and Jack are trying to do. You say you've made these choices to save the world from global warming but did not design a sustainable reactor and fuel cycle. You're going to make a lot of waste and the bigger problem is that most of it will be very difficult to deal with.

Does an "MSR done right" have to last for 30+ years? The differentiation I see in ThorCon and IMSR is an emphasis on regular maintenance/replacement and economies of scale. I don't see either saying their fuel cycle is the best; if anything their plans emphasize that incrementally better reactors can be used as they're available. I don't think you're subject to the same technological lock-in when your product has a useful life of less than 10 years.

I don't see how either design is prevented from a subsequent switch to:
A better moderator than graphite
Better neutronics from FLIBE salt

ThorCon might even be able to incorporate a pure cycle by placing reprocessing equipment in the silo hall.

It's a lot harder than that, Cthorm. You have to think a breeder reactor from the get-go. You design everything around that objective, and it shapes the choices you make, everything from layout to materials to processing to safety case.

You are NOT going to be able to "retrofit" an IMSR or a ThorCon to be an economic thorium breeder in the future. They will have to be completely rethought and redesigned.

I am designing LFTR to be the sustainable reactor that the world will need for millennia, and I am trying my best not to take shortcuts in the design. But it is slow hard work. Jack Devanney has apparently figured out how to get his team to work for free. He must know something about human motivation that has eluded me thus far.

Cyril R wrote:There seems to be rather a lot of it in low concentration ores and the ocean. Like, million year amounts, with Thorcons. That'd provide plenty of time to get a perfect reactor replacement.

It troubles me that you might actually believe that this is politically and socially feasible.

You need a long time because you know you're "punting" on the fuel cycle right now.